Caution labels are stuck to automobiles and home electric appliances for calling for attention in use thereof. On a caution label, printed is a direction such as a warning mark or a precaution note to observe in use; and such a caution label is stuck to products or product parts and is used for calling for attention to injury or fire in erroneous use. On a caution label, the printed direction must be deciphered irrespective of the adherend to which the label is stuck, and therefore a high-opacity base is used for the label.
Regarding automobile parts in an engine room, a caution label is stuck to a reserve tank, a fan tunnel, a battery tank, an air cleaner box, an engine cover, a belt cover, a fuse box, etc. For the above parts, used is resin for body weight saving, and in particular, a propylene-based resin is used from the viewpoint of the moldability and the cost thereof, and the resin is molded mostly according to an injection molding method. In the injection molding method, a resin is melted in a heating cylinder, then injected into the cavity of a closed mold at high temperature and under high pressure, and cooled and solidified in the mold to thereby form therein an article corresponding to the shape of the mold cavity.
Heretofore, as the caution label to be stuck to such injection-molded parts, a self-adhesive label is used. However, the self-adhesive label is problematic in that, when used for a long period of time, it may peel away from its edge owing to friction, vibration or impact shock, or in case where the label is forcedly peeled away, the entire label may peel away thereby failing in satisfactory attention-seeking purpose. In addition, when a self-adhesive label is stuck to an adherend and in case where the label is stuck to the just-molded adherend, then the molded adherend may shrink with time therefore bringing about some problems in that the label is swollen or the label surface is wrinkled; and therefore, the molded adherend must be stored as an intermediate stock until their shrinkage could settle.
As a method for solving these problems, employed is a technique of in-molding molding of integrally molding an adherend with a label. The method comprises previously inserting a label into a mold, and then injection-molding an adherend in the mold simultaneously with melt-adhering the label to the adherend (see Patent Reference 1, Patent Reference 2). As the label for in-mold molding of the type, there are known a gravure-printed resin film, a multicolor offset-printed synthetic paper (for example, see Patent Reference 3, Patent Reference 4), a synthetic paper comprising a heat-sealable layer having a porous surface and a print layer (see Patent Reference 5), etc.